infiltrate
Americanverb (used with object)
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to filter into or through; permeate.
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to cause to pass in by filtering.
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to move into (an organization, country, territory, or the like) surreptitiously and gradually, especially with hostile intent.
The troops infiltrated the enemy lines.
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to pass a small number of (soldiers, spies, or the like) into a territory or organization clandestinely and with hostile or subversive intent.
The intelligence agency infiltrated three spies into the neighboring country.
verb (used without object)
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to pass into or through a substance, place, etc., by or as by filtering.
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Pathology. to penetrate tissue spaces or cells.
noun
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something that infiltrates.
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Pathology. any substance penetrating tissues or cells and forming a morbid accumulation.
verb
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to undergo or cause to undergo the process in which a fluid passes into the pores or interstices of a solid; permeate
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military to pass undetected through (an enemy-held line or position)
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to gain or cause to gain entrance or access surreptitiously
they infiltrated the party structure
noun
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something that infiltrates
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pathol any substance that passes into and accumulates within cells, tissues, or organs
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pathol a local anaesthetic solution injected into the tissues to cause local anaesthesia
Other Word Forms
- infiltration noun
- infiltrative adjective
- infiltrator noun
- reinfiltrate verb
- uninfiltrated adjective
Etymology
Origin of infiltrate
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
That has not stopped Ukrainian President Volodymyr Zelensky vowing to infiltrate the messenger.
From Barron's • Mar. 23, 2026
According to Uson, the tumor's ability to infiltrate surrounding tissue is a major reason for the poor outlook faced by many patients.
From Science Daily • Jan. 30, 2026
It emphasized that they “can be exploited for security purposes in order to infiltrate foreign associations.”
From The Wall Street Journal • Dec. 10, 2025
There are fears that, now the rainy season has started, heavy metals still sitting in the mud will further infiltrate the land and waterways, causing a second wave of pollution.
From BBC • Dec. 2, 2025
“I took Rulean’s place first, absorbing some of his powers, before helping Aamon and then Gamigin infiltrate and replace the other two Uncles. It wasn’t very hard at all.”
From "Witchlings" by Claribel A. Ortega
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
